FEM Simulation of Cutting Process of Sheet Metals with Wedge Shape Punches.

Abstract

Cutting of a sheet metal by indentation of wedge shape punches is investigated as a process to achieve burr-free-cutting. Numerical simulations of the cutting process are done using a rigid plastic finite element code developed by the authors. Equivalent strain and hydrostatic stress distributions at the deformation region of the sheet are calculated, and the effects of wedge angle on the shape of the cut edge are discussed based on the calculated stress and strain states. To confirm the result of the finite element simulations, cutting experiments are carried out using a mild steel sheet of 3 mm in thickness, and the shape of the cut edge is observed using a scanning electron microscope. The experimental results show that the cutting mode depends very much on the wedge angle α and nose radius γ of punch; when the punch of γ=0.1mm and α=30 degree is used a sheet is separated by cutting, while when α=60 and 90 degrees ductile fracture is caused due to the secondary tensile force induced by the wedge indentation, and when α=120 degree brittle fracture is caused due to excessive work hardening during compression. When the nose radius of punch is increased from 0.1mm to 0.5mm, the deformation of sheet material between upper and lower punches becomes compression rather than cutting because of the suppression of the crack initiation and propagation from the punch nose portion. Therefore, when the punch of γ=0.5mm is used, the separated surface has a very thin flash. These experimental results are qualitatively in good agreement with the simulation results.